Haemophilus influenzae is a small, non-motile, Gram-negative coccobacillus. It is a respiratory pathogen that causes a wide spectrum of human infections, including: asymptomatic colonization of the upper respiratory tract (i.e. carriage); infections that extend from colonized mucosal surfaces to cause otitis media (inflammation of the middle ear), bronchitis, conjunctivitis, sinusitis, urinary tract infections and pneumonia; and invasive infections, such as bacteremia, septic arthritis, epiglottitis, pneumonia, empyema, pericarditis, cellulitis, osteomyelitis and meningitis. H. influenzae was the first bacterium for which a complete genome sequence was published [1].
H. influenzae strains are either capsulated (typeable) or non-capsulated (non-typeable), and there are six major serological types of capsulated strains (a to f). 95% of H. influenzae-caused invasive diseases are caused by H. influenzae type b (‘Hib’) strains. The most serious manifestation of Hib disease is meningitis, but the introduction in the 1980s of vaccines based on conjugated Hib capsular saccharides has hugely reduced incidence of this disease.
Although Hib infections can now be controlled by vaccination, other pathogenic H. influenzae strains remain a risk. For instance, non-typeable H. influenzae (NTHI) is responsible for otitis media (OM), particularly chronic and acute OM. While OM is rarely associated with mortality, it is associated with significant morbidity. Hearing loss is the most common complication of OM, with behavioural, educational and language development delays being additional consequences of early onset OM with effusion. Acute OM is the most common bacterial infection in children in the USA. The non-typeable H. influenzae biogroup aegyptius causes epidemic conjunctivitis and Brazilian purpuric fever (BPF) [2], with BPF having a mortality of up to 70%.
To date, antibiotics are the main tool against the spectrum of clinical entities known collectively as OM, but widespread use of antibiotics for OM has met with controversy due to the emergence of multiple-antibiotic resistant microorganisms. Progress towards a vaccine is slow due to an incomplete understanding of both the pathogenesis of OM and the immune response to it.
The genome sequence of the serotype d strain KW20 [1,3] has been useful for understanding basic H. influenzae biology, but it has not been so useful in countering pathogenic H. influenzae strains, as serotype d strains are generally not pathogens. Polypeptides from pathogenic non-typeable H. influenzae have been identified and investigated as vaccine candidates. Reference 4 discloses immunogenic polypeptides from a pathogenic non-typeable H. influenzae strain.
However, there remains a need for providing a vaccine that protects against a broad spectrum of Haemophilus influenzae strains. H. influenzae is a versatile microorganism with an improved ability to adapt to new niches and to cause a broad spectrum of disease. Fitness, virulence and colonization factors can change in order to allow the microorganism to adapt to different tissues and hosts. Therefore, potential antigens are subject to high selective pressure and, as a result, may have sequence variability among different strains.
Thus there remains a need to identify further and improved antigens for use in non-typeable Haemophilus influenzae vaccines, and in particular for vaccines which are useful against multiple NTHI-caused pathologies.
The database of genomes available at ncbi.nlm.nih.gov under genomes listed pathogenic and non-pathogenic Haemophilus influenzae genomes with as few as 2,500 proteins to as many as 4,000 proteins. However, such listings do not identify which are conserved across a significant fraction of the pathogenic NTHI, what are the conserved regions in the proteins that are so conserved, or which proteins among the thousands of potential proteins can be used in a vaccine to produce a sufficient immune response to protect against pathogenic NTHI which requires screening large numbers of proteins to identify the best candidates.
It is an object of the invention to provide further and better antigens and/or combinations which are efficacious in raising immune responses against different strains of H. influenzae, for use in the development of vaccines for preventing and/or treating infections caused by H. influenzae pathogens, in particular non-typeable H. influenzae. In particular, it is an object to provide polypeptides and combinations of polypeptides for use in improved immunogenic compositions and vaccines for preventing and/or in treating such infections, and in particular acute otitis media and chronic obstructive pulmonary disease (COPD). The polypeptides may also be useful for diagnostic purposes, and as targets for antibiotics.